To declare a bean, simply annotate a method with the @Bean annotation. You use this method to register a bean definition within an ApplicationContext of the type specified as the method's return value. By default, the bean name will be the same as the method name. (See bean naming for details on how to customize this behavior.) The following is a simple example of a @Bean method declaration:

@Configuration
public class AppConfig {

    @Bean
    public TransferService transferService() {
        return new TransferServiceImpl();
    }

}

The preceding configuration is exactly equivalent to the following Spring XML:

<beans>
    <bean name="transferService" class="com.acme.TransferServiceImpl"/>
</beans>                

Both declarations make a bean named transferService available in the ApplicationContext, bound to an object instance of type TransferServiceImpl:

transferService -> com.acme.TransferServiceImpl
                

When @Beans have dependencies on one another, expressing that dependency is as simple as having one bean method call another:

@Configuration
public class AppConfig {

    @Bean
    public Foo foo() {
        return new Foo(bar());
    }

    @Bean
    public Bar bar() {
        return new Bar();
    }

}                

In the example above, the foo bean receives a reference to bar via constructor injection.

Beans created in a @Configuration-annotated class supports the regular lifecycle callbacks. Any classes defined with the @Bean annotation can use the @PostConstruct and @PreDestroy annotations from JSR-250, see JSR-250 annotations for further details.

The regular Spring lifecycle callbacks are fully supported as well. If a bean implements InitializingBean, DisposableBean, or Lifecycle, their respective methods are called by the container.

The standard set of *Aware interfaces such as BeanFactoryAware, BeanNameAware, MessageSourceAware, ApplicationContextAware, and so on are also fully supported.

The @Bean annotation supports specifying arbitrary initialization and destruction callback methods, much like Spring XML's init-method and destroy-method attributes to the bean element:

public class Foo {
    public void init() {
        // initialization logic
    }
}

public class Bar {
    public void cleanup() {
        // destruction logic
    }
}

@Configuration
public class AppConfig {
    @Bean(initMethod = "init")
    public Foo foo() {
        return new Foo();
    }
    @Bean(destroyMethod = "cleanup")
    public Bar bar() {
        return new Bar();
    }
}

Of course, in the case of Foo above, it would be equally as valid to call the init() method directly during construction:

@Configuration
public class AppConfig {
    @Bean
    public Foo foo() {
        Foo foo = new Foo();
        foo.init();
        return foo;
    }

    // ...
}                    

	Tip
	When you work directly in Java, you can do anything you like with your objects, and do not always need to rely on the container!

By default, Configuration-classes use a @Bean methods name as the name of the resulting bean. This functionality can be overridden, however, with the name attribute.

@Configuration
public class AppConfig {

    @Bean(name = "myFoo")
    public Foo foo() {
        return new Foo();
    }

}